(Tom is a Visiting Scientist at the Southwest Fisheries Science Center in La Jolla, CA)

Cetaceans have long been highly prized by humans looking for a good source of food, oil and a whole host of other products. Cetaceans are attractive subjects for human exploitation because of their enormous size. Until the last few hundred years, their relatively inaccessible habitats made them difficult to hunt. Although there is evidence that prehistoric humans may have taken advantage of the fortuitous stranding of a fresh whale or dolphin on their shores, most cetacean species were relatively safe from large-scale human exploitation until recently.

The first known large-scale hunting of whales was by the Basques, starting in the first millennium AD. They hunted in the Bay of Biscay bounded on the east by the west coast of France and on the south by the north coast of Spain. They mainly targeted the North Atlantic right whale (Eubalaena glacialis), and were so effective in killing so many of this species that their recovery is in doubt today. Norse and Icelandic whalers also hunted in the North Atlantic, and the Japanese began their culture of whale hunting in the 1600s. In the 1700s, the “Yankee whaling” era began, focusing largely on sperm whales (Physeter macrocephalus). This led to the United States becoming a major player in the commercial whaling game. In the late 1800s, the development of steam-powered vessels and the exploding harpoon ushered in the modern era of commercial whaling. Fast-swimming Balaenoptera species, such as the rorquals (blue, fin, sei, Bryde’s and minke whales) were now within the realm of commercial whalers. It did not take long for whalers to decimate species after species, starting with the largest and working their way down the list, to “commercial extinction” (the point at which it is no longer financially viable to continue the hunt).

However, the public perception that all large whales are endangered is wrong. The truth is that most large whales are no longer commercially hunted and many are recovering from past exploitation—with major exceptions being the North Atlantic and North Pacific right whale (E. japonica) species. The real serious conservation problems now lie with several of the smaller cetacean species. The vaquita (Phocoena sinus), Indus susu (Platanista gangetica minor), North Island Hector’s dolphin (Cephalorhynchus hectori maui) and Atlantic humpback dolphin (Sousa teuszii) are some of the most severely endangered species.

In recent decades, the direct killing of whales and dolphins has become much less important, and the indirect deaths of dolphins and porpoises in particular have increased dramatically. There is now no doubt that more cetaceans die incidentally in fishing nets each year than from any other threat, including whale and dolphin hunting.

In the last few decades, we have also seen the development of other major threats to these animals in the form of habitat degradation, environmental contamination, noise pollution (including naval sonars), and even live captures for captive display and research. Despite a number of populations of cetaceans in specific regions being annihilated by humans (e.g., the Atlantic gray whale by commercial whaling), it is only recently that an entire cetacean species has gone extinct at the hands of humans. However, several other species, such as the vaquita in Mexico and Northern Hemisphere right whales, are now on the verge of that same fate.

The baiji, found only in the Yangtze River and some connected lakes in China, was declared to be probably extinct in 2007, after an extensive survey of nearly their entire known range turned up no sightings or acoustic detections. Besides incidental deaths in fishing gear and problems of severe pollution, the baiji suffered from general habitat loss and degradation. Their environment was severely degraded from rapid modification of the river for human use, with little or no concern for its original inhabitants. The Chinese Government had been warned of this for decades and ignored the pleas of the outside world.

Closer to home for those of us in the U.S., the vaquita seeks out a precarious existence in the northern Gulf of California, Mexico. This small porpoise species has serious problems with incidental catches in gillnets (and much less, so trawls). There are other potential threats as well, but they probably pale in comparison to the fishery entanglement problems.

The vaquita population numbers no more than a few hundred (the current best estimate is about 150). The Mexican government appears to be taking the situation very seriously, and is making an attempt to remove gillnets from the vaquita’s range. Although the species is still in serious trouble, there is some reason for cautious optimism about the vaquita’s future, but we must move fast to avoid a repeat of the baiji tragedy.

One thing that is important to remember about endangered species is that some “Endangered Species Lists” include species mainly for political reasons, and their legal status listing may not be accurate. Thus, there is a difference between Endangered (the official status listing, with a capital E) and endangered (the true status of a species, with a lower-case e). For example, the sperm whale is listed as Vulnerable by the International Union for the Conservation of Nature (IUCN) and Endangered by the US Government, yet it is globally distributed, numbers in the hundreds of thousands and many populations are quite healthy. Thus, the sperm whale is not really endangered.

Nonetheless, several cetacean species, and many other populations, are genuinely in danger of extinction in the next decade or two. This is a sad statement on the depths of human greed and carelessness for the natural environment. It is my hope that this article will help people appreciate the diversity and fragility of the world’s marine mammals, and will inspire them to work towards their long-term protection.

IUCN Classifications of Degrees of Threat:By classifying species into categories of threat, conservation recommendations can be made based on the status of the species, its abundance, and distribution.

Extinct (EX): There is no reasonable doubt that the last individual has died.

Extinct in the Wild (EW): Known only to survive in captivity or as a naturalized population well outside the past range.

Critically Endangered (CR): Facing an extremely high risk of extinction in the wild.

Endangered (EN): Facing a very high risk of extinction in the wild.

Vulnerable (VU): Facing a high risk of extinction in the wild.

Near Threatened (NT): Not in one of the categories above, but is close to qualifying for or is likely to be in a threatened category in the near future.

Least Concern (LC): Not in one of the categories above. Widespread and abundant taxa are included in this category.

"The gray, sei, blue, and fin whale species are not endangered on a global scale, but isolated populations of these species have been severely depleted and face some danger of extinction. Sadly, there have probably been several cetacean populations that have been exterminated by humans before they were even documented by scientists. In fact, even today for most species of cetaceans, global population structure is very poorly known."